Key takeaways

  • An anion gap blood test measures the acid-base and electrolyte balance in the blood. A low anion gap is very rare and often results from a laboratory error, but it may indicate hypoalbuminemia, a condition involving low albumin levels due to inflammation, malnutrition, liver or kidney disease, or certain electrolyte imbalances.
  • Symptoms depend on the underlying cause and may include fatigue, nausea, headache, rapid heart rate, and shortness of breath. Treatment focuses on addressing the health issue causing the imbalance.

A low anion gap results from an imbalance in the body’s pH levels. Healthcare professionals identify this “gap” by examining the results of a blood test that measures electrolyte levels.

To maintain health and function, the body needs a pH balance. This refers to the blood’s balanced levels of acids and alkali, or bases. Electrolytes are substances in the blood that carry an electrical charge and help maintain the body’s pH balance, and are vital to many other functions.

A person with a pH imbalance may have high acid levels, called “acidosis,” or high bases, known as “alkalosis.” A pH imbalance is a serious concern and indicates an underlying health condition.

Read on to learn about what can cause a low anion gap, symptoms, treatment options, and more.

Typical anion gap readings range from 4 to 12 millimoles per litre (mmol/L). Readings outside this range may indicate a pH imbalance, which can stem from various health issues.

Having an anion gap reading in the low range is very rare, and it may stem from a laboratory error. A doctor usually orders a second test if an electrolyte blood test shows a low anion gap.

Hypoalbuminemia

While a low anion gap is rare, a condition called hypoalbuminemia can cause a low anion gap reading.

Hypoalbuminemia involves having low levels of an essential protein called albumin in the blood. It can occur because of inflammation throughout the body.

Some specific causes of hypoalbuminemia include:

A low anion gap can occur alongside symptoms of alkalosis, or too little acid the blood. Symptoms may include:

  • hand tremors
  • muscle twitching
  • irritability
  • arrhythmia (irregular heartbeats)
  • nausea
  • vomiting
  • numbness or tingling in the hands, feet, or face

People may also experience symptoms consistent with the underlying condition affecting blood pH. For example, a person with alkalosis due to hypoalbuminemia may experience:

Treatments can address the health issue responsible for an abnormal anion gap reading.

Measuring the anion gap alone cannot confirm any diagnosis, so a doctor will likely order a variety of other tests before making a diagnosis and recommending a suitable treatment plan.

Anyone concerned about a high or low anion gap reading should discuss the possible cause with their doctor.

Low anion gap test results are often due to testing errors and are incredibly rare. However, they may indicate hypoalbuminemia. If further tests confirm a person has a low anion gap, medical assistance is essential.

Multiple myeloma, a type of bone marrow cancer, can cause a low anion gap. Certain cancer treatments may also impact potassium levels, leading to alkalosis.

Treating the underlying cause of an anion gap, either high or low, will help to stabilize blood pH levels. It is important to speak with a medical professional for guidance on suitable treatments.

A low anion gap reading is very rare, and it often results from a laboratory error. As a result, a doctor who finds a low reading typically orders a second test.

In some cases, hypoalbuminemia can lead to a low anion gap. It may cause symptoms such as hand tremors, muscle twitching, irritability, nausea, and vomiting.

A doctor can provide more specific information about the likely cause of a low or high anion gap reading. If they confirm a low anion gap, they will likely order more tests to determine the underlying cause and then advise on suitable treatments.